1. Field of the Invention
The present invention relates to a magnetic head device which is to be mounted in a hard disk drive or the like. More particularly, the invention relates to a magnetic head device in which a good electrical connection between a slider and its support is ensured and electrostatic discharge is prevented from occurring in a thin-film element for writing and/or reading provided on the slider and to a method for making the magnetic head device.
2. Description of the Related Art
A conventional magnetic head device which is to be mounted in a hard disk drive or the like has, for example, a structure shown in FIG. 21.
The magnetic head device includes a slider 1 and a support 2 for supporting the slider 1.
The slider 1 is composed of a ceramic or the like. As shown in FIG. 21, a thin-film element 3 for writing and/or reading is provided on the trailing side of the slider 1.
The support 2 includes a load beam 4 and a flexure 5. The load beam 4 is composed of a leaf spring material, such as stainless steel, and includes bent sections 4a having rigidity on both sides of the front end. A predetermined elastic force can be displayed at the base end of the load beam 4 (not shown in the drawing).
As shown in FIG. 21, a pivot 6 protruding toward the flexure 5 is disposed in the front portion of the load beam 4, and the slider 1 abuts against the pivot 6 with the flexure 5 therebetween.
The flexure 5, for example, includes a fixed section 5a and a tongue 5b. The fixed section 5a and the tongue 5b are joined to each other at the trailing end. The tongue 5b is separated from the fixed section 5a except at the joint to the fixed section 5a, and the leading side of the tongue 5b is a free end. The fixed section 5a is bonded to the rear face of the load beam 4 with an adhesive or the like. The tongue 5b is disposed so as to be movable under the pivot 6, and the slider 1 is bonded to the rear face of the tongue 5b with an adhesive layer 8.
The adhesive layer 8 disposed between the tongue 5b and the slider 1 is, for example, composed of a thermosetting adhesive, a conductive resin, etc.
The conductive resin is disposed between the tongue 5b and the slider 1 in order to dissipate static electricity charged in the slider 1 due to friction, etc., toward the support 2.
FIG. 22 is a partially enlarged sectional view showing the slider 1 before being bonded to the tongue 5b. 
As shown in FIG. 22, a conductive resin 9 is partially applied onto the tongue 5b and a thermosetting resin (not shown in the drawing) is also applied onto the tongue 5b, and then the slider 1 is placed on the tongue 5b. By subsequent heating, etc., the slider 1 is bonded to the tongue 5b. 
As shown in FIG. 22, an insulating layer 10, which is formed due to natural oxidation or the like, is disposed on the tongue 5b. Accordingly, the conductive resin 9 is applied onto the insulating layer 10.
The conductive resin is described, for example, in Japanese Unexamined Patent Application Publication No. 9-22518 (Patent Literature 1) and Japanese Unexamined Patent Application Publication No. 2002-343048 (Patent Literature 2).
According the experiments, which will be described below, when a low voltage, for example, 0.5 V or less, is applied between the slider 1 and the support 2, the resistance is significantly high at several megohms. That is, the electrical connection between the slider 1 and the support 2 is extremely poor.
The reason for this is that the insulating layer 10 is disposed on the tongue 5b. Consequently, even if the conductive resin 9 is placed between the tongue 5b and the slider 1, a good electrical connection is not achieved between the slider 1 and the tongue 5b, and static electricity charged in the slider 1 cannot be effectively dissipated toward the support 2.
As a result, as shown in FIG. 21, when the slider 1 flies above a recording medium D with a short spacing from the surface of the recording medium D and if an electrical potential difference occurs between the slider 1 and the recording medium D, a discharge occurs from the slider 1 to the recording medium D, i.e., a short circuit occurs between the slider 1 and the recording medium D. Thereby, an overcurrent flows through the thin-film element 3, resulting in electrostatic discharge (ESD) of the thin-film element 3.
Although Patent Literatures 1 and 2 describe the conductive resin, neither of them describes the insulating layer formed under the conductive resin. Therefore, it has not been disclosed how to secure an electrical connection between the slider 1 and the tongue 5b through the conductive resin 9 and the insulating layer 10.